Review Article

Inhibitory Potential of Medicinal Plants Against Viral Pathogens and their Putative Modes of Action

Muhammad Akram1, Anirban Mandal2*, Mehwish Iqbal3, Arindam Mukherjee4, Ritika Bandyopadhyay5, Surendar Rangasamy6, Rida Zainab1, Muhammad Talha Khalil1, Pragnesh Parmar7 and Umme Laila1

1Department of Eastern Medicine and Surgery, Directorate of Medical Sciences, GC University Faisalabad, Pakistan; 2Department of Microbiology, Mrinalini Datta Mahavidyapith, Kolkata, India; 3Institute of Health Management, Dow University of Health Sciences, Karachi, Pakistan; 4Department of Botany, Mrinalini Datta Mahavidyapith, Kolkata, India; 5Department of Microbiology, Barrackpore Rastraguru Surendranath College, Kolkata, India; 6Department of Community Medicine, Sri Venkateshwaraa Medical College Hospital and Research Centre, Puducherry, India; 7Department Forensic Medicine and Toxicology, AIIMS, Bibinagar, Telangana, India.

Received | May 10, 2023; Accepted | December 20, 2023; Published | December 28, 2023

*Correspondence | Anirban Mandal, Department of Microbiology, Mrinalini Datta Mahavidyapith, Kolkata, India; Email: anirbanmondal31@gmail.com

Citation | Akram, M., A. Mandal, M. Iqbal, A. Mukherjee, R. Bandyopadhyay, S. Rangasamy, R. Zainab, M.T. Khalil, P. Parmar and U. Laila. 2023. Inhibitory potential of medicinal plants against viral pathogens and their putative modes of action. Hosts and Viruses, 10: 58-71.

DOI | https://dx.doi.org/10.17582/journal.hv/2023/10.58.71

Keywords: Viral infections, Complementary and alternative medicines, Antiviral molecules, Medicinal plants, Herpes simplex virus, Influenza A virus

Copyright: 2023 by the authors. Licensee ResearchersLinks Ltd, England, UK.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Introduction

Plants have assisted humans as a significant source of drugs and foods. Worldwide a large part of communities depends upon herbal medicines to meet their health necessities, either alone or in combination with other CAM (complementary and alternative medicines) (World Health Organization, 2013), (Jonas et al., 2013). In modern days, the study and use of plant products in medical science are increasing day by day. For example, in 2017, the use of botanical products has increased rapidly 8.5 percent (in contrast with the last year) in United States, accomplishing an approximated amount of 8 billion Unites states dollar (Smith et al., 2018). With respect to pharmaceutical companies, frequent compounds acquired from sources of plant have extensively been identified to have pharmacological properties, and in history plants have produced numerous significant medicines for ingestion into human body, since morphine, used as the contemporary artemisinin and paclitaxel in early 19th century. In case of diabetes mellitus, research stated that the compounds of Amadori rearrangement acquired from the onion extract that is thermally-processed were capable of repress absorption of carbohydrate by means of reducing intestinal sucrose, thus inhibiting the postprandial rise in blood glucose (Kang et al., 2018). Conversely, one of the studies demonstrated that in vitro defensive property of gomisin N (acquired from the plant of Schisandra chinensis) conflicting to cannabinoid type-one receptor-prompted disablement of insulin signaling, in addition to in vivo influence of the composite on gluconeogenesis in high-fat-diet-prompted-obese mice (Nagappan et al., 2018). Moreover, procyanidin A2 and catechin were capable of restraining inflammation of nervous system in amyloid managed microglial cells of BV-2 cell line (Tang et al., 2018). A segment of glucan produced from the stem of Pleurotus eryngii restrained inflammation in a sulfated polysaccharide, named DSS-tempted mouse model of IBD. The section of glucan exhibited downregulation outcomes on levels of Interferon gamma and Macrophage Inflammatory Protein 2 (Vetvicka et al., 2018). In another research it was revealed that the flavonoids segregated from Chinese liquorice (Glycyrrhiza glabra) could encourage distinction of malignant melanoma B16-F10 cells or stimulate apoptosis (Zheng et al., 2018). Moreover, the pharmacokinetics of the liver protective triterpenic acids (TAs) acquired from the fruits of jujube by using an ultra-high performance liquid chromatography tandem mass spectrometry method to investigate the samples of plasma in normal and carbon tetrachloride-managed rats (Li et al., 2018).

A sequence of cinnamamide products have noteworthy anti-tubercular, anti-microbial, and anti-mycotic activities (Pospisilova et al., 2018). Discovering therapeutic strength of botanicals is a prehistoric concept. Individuals from all landmasses have extensively applied poultices and drank teas of hundreds or thousands, of aboriginal plants, antedate to early history. There is a proof that Neanderthals (an extinct species of archaic humans) existing 60,000 years ago presently Iraq utilized herbs for instance Alcea rosea (hollyhocks) (Stockwell, 1988; Thomson, 1978), these botanicals are still extensively utilized in ethnomedicine all over the world. After the beginning of antibiotics in the duration of 50s, the usage of plant derived products as anti-bacterial has been practically missing. After a decline in that speed in modern decades, the pace is yet once more advancing as researchers recognize that the efficient life expectancy of any antibiotic is bounded. Global expenditure on discovering novel anti-virulent mediators (counting vaccines) is supposed to escalate by sixty percent from the expenditure levels in 1993 (Cowan, 1999). Plant sources, are also being examined. Subsequently, the people are becoming progressively conscious of complications with the abuse and over prescription of conventional antibiotics. Additionally, numerous people are concerned in having extra autonomy in terms of their therapeutic care. A large number of plant compounds is easily accessible without doctor’s prescription from suppliers of herbs and self-medication with these elements is usual. The use of plant-derived products, in addition to other substitutive forms of medicinal managements, is appreciating great admiration in the late 1990s. Previously in this decade, around 1/3rd of people examined in the US consumed no less than one “unusual” therapy in the last year (Eisenberg et al., 1993).

History

It is approximated that there are 50,200 to 500,000 species of botanicals on this planet (Borris, 1996). Comparatively minor percentages (1-10%) of plants are consumed in diet by both animal and humans. Hippocrates (the father of medicine) stated three hundred to four hundred healing plants (Thomson, 1978). Pedanius dioscorides (a Greek physician and botanist) inscribed De Materia Medica, a catalog of medicinal herb became the model for modern dispensary. The Bible proposes explanations of almost thirty medicinal plants. In fact, myrrh and frankincense possibly relished their position of great value because of their therapeutic properties. Stated to have germ-killing characteristics, they were also used as mouthwashes. The decline of prehistoric civilizations anticipated western developments in the interpretating of medicinal botanicals, with ample of the records of plant medicament being misplaced or demolished (Stockwell, 1988). Throughout the middle ages, the Arab nation endured to unearth their particular older works and to construct upon them. Certainly, cultures of countries under Asia continent were also engaging in assembling their personal pharmacopoeia. In western regions, the era of Renaissance saw a restoration of prehistoric medicine, which constructed from the herbal medicines. History of North America’s medicinal plant usage follows 2 strands one was to utilize native cultures (Native Americans), dating from ancient history (Weiner, 1980), and the another one was a substitutive motion among Americans of European origin, beginning in the 19th century. American utilization of indigenous medicinal plant has been evaluated broadly in a sequence of articles by Moerman (1996). He stated that after utilizing 1,625 species of plants by numerous aboriginal American groups as food, 2,564 species used as medicines (Cowan, 1999). Botanicals have nearly infinite capacity to produce aromatic constituents, like phenols or their derivatives (Geissman, 1963). Throughout the seventeenth and 18th centuries understanding of plant originated drugs developed speedily. Though, efforts to discover the dynamic molecule(s) were continuously ineffective. In 1817, a huge revolution was happened when Friedrich Sertürner, a German researcher extracted morphine from the seeds of Papaver somniferum (Schmitz, 1985) and it was becoming the 1st dynamic discovery of herbal medicine. Vigilant exploration of chemicals reported morphine to be the alkaloid. Quinine, a plant product of Cinchona officinalis, was the first efficient management of malaria; it continued to be the well-known medicine to manage this ailment well until into the 1940s and is still used in numerous progressing countries (Reyburn et al., 2009). The healing characteristics of Cinchona officinalis, were initially revealed by the Quechua Indians of Bolivia and Peru, consequently this information was brought to European regions by the Jesuits. The efficiency of bark of cinchona in managing malaria rapidly became the most appreciated raw materials transported from Peru to Europe. Quinine, was also secluded from both the cinchona bark and termed by Pierre Pelletier and Joseph Bienaime in 1820. Whereas a number of total combinations of quinine have been described (Woodward and Doering, 1945) additional important constituent from organic product used in biomedicine is salicin, extracted from willow bark and is recognized in 1838 by Johannes Buchner, the bark of which had initially been used as an analgesic by the early Greeks. It was then researched and used by the Bayer Company as aspirin. The segregation of other important herbal products shortly followed, hence the 1800’s became a golden age for plant derived product research (Yun et al., 2012).

Viral diseases

Infections of viral origins continue to be a foremost reason of ill health and death globally. From all of them the most destructive virus-related diseases are severe acute respiratory syndrome Ebola, Influenza, and Acquired Immuno-Deficiency Syndrome. For example, Influenza is accountable for more than 3 million new patients of severe ailment, and approximately 0.5 million fatalities annually (Gasparini et al., 2012; Nováková et al., 2018). Distressingly, the quantity of patients identified with viral diseases is growing each year with increased transplantations of organ, blood transfusions, and the usage of infected subcutaneous syringes. Standard antiviral medicines for instance ribavirin and interferon are efficient in vitro against numerous viruses, however frequently they are not completely successful in humans. Currently 90 distinct anti-viral agents exist (Soltan and Zaki, 2009; Brijesh et al., 2009) and they can merely manage a range of viruses; these viruses include HIV, herpes simplex virus, influenza viruses, human alphaherpes virus 3, hCMV and hepatitis viruses. At present, appropriate therapy against a certain number of viruses, and vaccination is surrounded to mumps, hepatitis A and human alphaherpes virus 3 (Nováková et al., 2018). Additionally, these agents are unsuccessful and expensive most of the times because of viral resistance and can be the source of unwanted effects. Keeping that in notice, organically established pharmacotherapy can be an appropriate substitute for managing viral illnesses.

Antiviral properties of plant products

Plant product against herpes simplex virus (HSV): Herpes simplex viruses with double-stranded DNA as genetic material, a highly contagious viruses that cause frequent ulceration in both humans and animals of all age groups. Botanicals may be another significant option for HSV treatment as they are used in a variety of mechanisms and help in reducing the development of antiviral resistance. An extensive diverse plant from different geographical regions have been studied against herpes simplex viruses and showed varying degrees of antiviral activity. Aqueous leaf extract of Melia azedarach contains antiviral molecule meliacine inhibited the lifecycle of herpes simplex virus type 1 (HSV-1). At non-toxic concentration, meliacine blocked HSV-1 infection through suppression of synthesis of some late infected-cell polypeptides (Villamil et al., 1995). The naked nucleic acids and capsids of HSV-1 could not be enveloped by a golgi-derived membrane in presence of meliacine (Alche et al., 2002). Geraniin and 1, 3, 4, 6-tetra-O-galloyl-beta D-glucose found in acetone extract of Phyllanthus urinaria suppress HSV-1 replication (Yang et al., 2007). In laboratory experiment, it was showed that aqueous root extract of Carissa edulis also has potent antiviral activity against both resistant and wild type strains of HSV (Tolo et al., 2006). According to a report, it was demonstrated that bioactive molecules, andrographolide and other derivatives such as neoandrographolide and 14-deoxy-11, 12-didehydroandrographolide from Andrographis paniculata have anti-HSV-1 activity (Wiart et al., 2005). A semi-synthetic compound of andrographolide (3, 19-isopropylidene andrographolide) showed inhibitory activity against HSV entry (Seubsasana et al., 2011). Mangiferin, an effective component of Anemarrhena asphodeloides, has antimicrobial properties along with effective antiviral property against this virus (Du et al., 2018). According to previous studies, aqueous extract of Moringa oleifera and methanol extract of Salvia rosmarinus leaves at a specific concentration can inhibit the growth of herpes simplex type 1 and type 2 (Anwar et al., 2007; Kriesel et al., 2005). These two plant extracts have antiviral properties because of the presence of flavonoid compound beta-amyrin and phenolic compound ferruginol which showed their antiviral properties by inhibiting lipid peroxidation, hindering replication of the viruses, destabilizing the lipid envelope of virus and hampering with adsorption and cell entry of virus (Jung, 2014). In some studies, it was also proved that there are some plants like Actium lappa, Calendula officinalis and Geranium robertianum may have different ways to inhibit the growth of HSV-1 (Corina et al., 1999). There are some plants like Abbottina rivularis, Bergenia ciliata, Cassiope fastigiata and Tillandsia linearis showed greater anti-HSV-1 activity, whereas extracts from Cotoneaster integrifolius, Clinopodium umbrosum, Oxytropis williamsii, Rhododendron anthopogon and Rubus foliolosus showed moderate to low anti-HSV-1 activity (Rajbhandari et al., 2007).

Plant product against corona virus: Since the outbreak of COVID-19, different indigenous herbal medicines have been used separately or with the conventional drugs in combination treatment to treat patients with SARS-CoV-2 (Mandal et al., 2022). Common spices with immunity bootstring properties present in our daily diet like garlic, turmeric, red pepper, and fenugreek have some antiviral property (Cardoso, 2022). There are almost eighteen antiviral compounds present in garlic oil, among them, leptin have the potentiality to prevent SARS-CoV-2 virus infection (Donma and Donma, 2020). Many antiviral compounds present in Ferula asafetida bind with the human ACE2 receptor and inhibit the viral entry within the host cell (Rajapaksa et al., 2020). There are some phytochemicals like quercetin and its derivatives can inhibit corona virus replication (Cardoso, 2022). Glycyrrhizin (GR) found in the root extract of Glycyrrhiza glabra has antitumor, antidiabetic, antioxidant, anti-inflammatory, hepatoprotective and antiviral properties. Glycyrrhizin is able to reduce the infection of SARS-CoV by inhibiting viral replication, penetration and adsorption (Baillya et al., 2020). Another antiviral molecule, glycyrrhizic acid isolated from the same plant is able to interact with spike glycoprotein of SARS-CoV and block the viral entry (Hoever et al., 2005). Four phyto compounds, including neoandrographolide, andrographolide, 14-deoxy andrographolide, and 14-deoxy 11, 12-didehydroandrographolide from Andrographis paniculata impeded coronaviruses life cycle by blocking the activity of non-structural proteins, papain-like protease and RNA dependent RNA polymerase. Among those phytocompounds, neoandrographolide have high affinity against SARS-CoV-2 infection (Murugan and Jeyakanthan, 2020). Molecular docking analysis showed that andrographolide can suppress Mpro of SARS-CoV-2 activity (Enmozhi et al., 2021). Similarly, withanolides isolated from Withania somnifera also able to inhibit the activity of Mpro of SARS-CoV-2 (Tripathi et al., 2021). Another important medicinal plant, Curcuma longa inhibits 3-CL protease which is one of the most important enzyme of coronavirus (Mandal et al., 2021). For all these beneficial activities, Ministry of Ayush, Govt. of India has approved Nilavembu Kudineer, a multiherbal formulation consisting of A. paniculata, Z. officinale, S. album in addition with other herbs act as a prophylactic add-on for COVID-19 (Khuntia et al., 2022). Phytocompounds like, isoflavone extracted from Psorothamnus arborescens, methyl rosmarinate from Hyptis atrorubens, myricitrin from Myrica cerifera, myricetin 3-O-beta-D-glucopyranoside from Camellia sinensis, amaranthin from Amaranthus tricolor and licoleafol from Glycyrrhiza uralensis are effective against SARS-CoV-2 (Qamar et al., 2020). Quinine extracted from the bark of Cinchona tree has potentiality to inhibit the growth this virus (Singh et al., 2020). Phyto compounds present in the leaves of Azadirachta indica, like, nimbidin, nimocinol, nimbolide, nimbinene, isomeldenin, nimbandiol, meliacinanhydride, and zafaral showed antiviral activity against coronavirus (Baildya et al., 2020). In in silico study, it was showed that luteolin-7-O-glucuronide and chlorogenic acid extracted from Ocimum sanctum likely binds to Cys145 of Mpro of SARS-CoV-2 and suppress the enzymes activity (Mohapatra et al., 2020). Phytocompounds such as berberine, cardiofolioside B, tinosponone, tembetarine, xanosporic acid present in Tinospora cordifolia, also have antiviral properties. Among those compounds, tinosponone acts as a potent inhibitor of Mpro of SARS-CoV-2 (Krupanidhi et al., 2020).

Plant product against human immunodeficiency virus: HIV has claimed ~40.4 million lives since the start of the epidemic (UNAIDS, 2022 fact sheet). There has been profound progress in the field of anti-HIV drug development that definitely restrained the progress of the disease and increased the life span of infected individuals. However, certain drawbacks still persist like emergence of drug resistant viral strains due to lifelong administration of HAART and absence of any vaccine so far (Shafer and Schapiro, 2008). There are number of plants that are used as herbal remedies against various viral infections, including HIV and are widely used as an essential part of traditional medicine (Mukhtar et al., 2008; Kurapati et al., 2016; Dhama et al., 2018; Mandal et al., 2020). For example, in laboratory experiment, it was proved that bioactive compounds extracted from Phyllanthus amarus (Notka et al., 2004), water/alcohol extract from Phyllanthus niruri (Qian-Cutrone et al., 1996), rosamultin from Rose rugosa (Park et al., 2005), aqueous extract of dried rose flowers (Fu et al., 2006), water and methanol extracts of Rosa damascene (Mahmood et al., 1996) have anti-HIV activities by blocking HIV-1 attachment, integration, reverse transcription and protease activity of this virus. The n-butanol extracts of Bridelia micrantha (family Euphorbiaceae) in IC50 of 7.3μg/ml showed antiviral activity against the RDDP function of HIV-1 RT (Bessong et al., 2006). The extracts of seed of Areca cutechu, and bark of Saruca indica, Eugenia jambohnu, Terminalia arjuna, Arecatannin B1, a procayanidin, extracted from Areca catechu (Kusumoto et al., 1995) and peyssonol A and B, two sesquiterpene hydroquinones from the red sea algae Peyssonelia species (Loya et al., 1995) showed inhibitory activity on HIV-1 PR. Calanolide- a plant derived compound acting as non-nucleoside analogues and suppressed human immunodeficiency virus replication (Xu et al., 2000). Phytosterol, β-sitosterol-3-β-D-glucopyranoside isolated from the roots and bark parts of Aleurites moluccana capsule, a conventional Hawaiian medicine worked on herpes viral infections, also act on HIV-1 (Ashrafi et al., 2022). Aqueous extract of the leaves of Pluchea indica has antiviral properties against HIV-1 (Locher et al., 1996). Extracts from leaf part of Scaevola tacadda and root part of Acorus calamus showed antiviral activity against reverse transcriptase enzyme of HIV-1 (Silprasit et al., 2011). Betulinic acid and its derivatives derived from Betula utilis commonly known as Bhojpatra in India significantly inhibited HIV-1 entry and protease enzyme activity (Singh et al., 2012; Lee, 2004). Cafeic acid, chlorogenic acid and 3,4-di-O-cafeoylquinic acid extracted from Bidens pilosa (known as xian feng cao) potentially inhibited HIV integrase (Xuan et al., 2016). Secomet-V, isolated from Trifollium species showed effectivity against HIV and some other viruses including human papillomavirus, influenza, HBV and HCV (Kotwal et al., 2005). Cyanovirin N, a 11-kDa protein isolated from the blue green algae, cyanobacterium Nostoc ellipsosporum inhibits HIV-1 infection by interacting with chemokine receptors, gp120 and inhibits entry of HIV (Clercq 2000). Shephagenins A and B, hippophaenin A and strictinin isolated from the leaf extract of Shepherdia argentea showed a remarkable antiviral activity against HIV-1 reverse transcriptase (Yoshida et al., 1996). Baicalein, a flavonoid purified from Scutellaria baicalensis showed anti-HIV-1 activities by interfering with the envelope proteins with chemokine co-receptors and blocking viral entry into the target CD4 cells (Li et al., 2000). Oligostilbene dibalanocarpol, purified from leaves extract of Hopea malibato, has antiviral activity against this virus (Dai et al., 1998). Inophyllum, calanolide A and coumarins isolated from the terrestrial plants of Calophyllum inophyllum, Calophyllum lanigerum, Calophyllum teysmannii and Calophyllum cerasiferum act on HIV-1-RT (Currens et al., 1996). Malva sylvestris also has the antiviral properties against reverse transcriptase enzyme of HIV (Benso et al., 2021). Catechin, lauric acid, capric acid or myristic acid extracted from Cocos nucifera, has antiviral properties by disrupting the viral membrane or by interfering with the virus maturation process (Mandal et al., 2011; Lima et al., 2015). α-Mangostine, a xanthone, polyphenolic compound found from Garcinia mangostana inhibits the activities of reverse transcriptase, protease of HIV-1 or by interfering with other replication processes (Bernal et al., 2015). Mangifera indica employed its antiviral activity because of the presence of xanthones and mangiferine which are interfering with the replication of the virus (Parvez, 2016). Fruit seeds extract of Nephelium lappaceum able to inhibit the HIV-1 reverse transcriptase activity. Two most important antiviral compounds, geraniin and hexadecanoic acid present in Nephelium lappaceum, blocks viral replication and inhibits HIV-1 infection to the host cell (Monrroy et al., 2020). Kaempferol, kaempferol 3-O-β-D-glucuronopyranosyl methyl ester, naringenin 7-O-β-D glucopyranoside, quercetin 3-O-β-D-glucuronopyranosyl methyl ester, resveratrol, caffeic acid, and scirpusins A and B found in Vitis vinifera are active against multiple RNA virus including HIV (Gaafar et al., 2019).

Plant product against viral hepatitis: Hepatitis viruses cause both severe to persistent liver illness, including liver misfunctioning, liver fibrosis and hepatocellular carcinoma etc., affect about several billions of the world’s population and it has been reported that a number of plant products with diverse chemical classes have antiviral activities against this virus (Ganta et al., 2017) such as plants belonging to the genus Phyllanthus of the family Euphorbiaceae has antihepatitic activity. In a study, it showed that different species of Phyllanthus, i.e., P. amarus, P. niruri and P. urinaria have antihepatitic B properties (Wang et al., 1995). In the molecular biology, it was revealed that the antiviral properties of P. amarus act on HBV polymerase activity and mRNA transcription by interacting with HBV enhancer I and C/EBP alpha and beta transcription factors (Ott et al., 1997), the ethanolic extract of P. nanus showed its antiviral activity on expression of several genes specifically annexin 7 (Lam et al., 2006). Similarly, the methanolic extracts of Acacia nilotica, Embelia schimperi, Valeriana wallichii, Boswellia carterii, Quercus infectoria, Trachyspermum ammi and aqueous extracts of Piper cubeba, Syzygium aromaticum, and Quercus infectoria also have antihepatitic properties (Ganta et al., 2017; Hussein et al., 2000; Mandal and Hazra, 2023). Some plant derived molecules such as catechin, polysterols, glycyrrhizin, silymarin also showed antihepatitic C activity (Jassim and Naji, 2003).

Plant products with broad spectrum antiviral activity: Complexes and constituents with antiviral activity exists in numerous plants, for instance, rutin, a flavonoid glycoside present in a range of botanicals, effective against herpes simplex virus-1, herpes simplex virus-2 (Yarmolinsky et al., 2012), influenza A virus (Ibrahim et al., 2013), and parainfluenza type-3 virus (Orhan et al., 2010). Quercetin, is a plant chemical that is found in ample quantity in plants and may reduce the multiplication of numerous viruses: Rhinovirus (Ganesan et al., 2012), influenza virus (Wu et al., 2015), dengue type-2 virus (Zandi et al., 2011), herpes simplex type-1 virus, adenovirus (Chiang, 2003), poliovirus (Neznanov et al., 2008), RSV, EBV (Lee et al., 2015), MAYV (dos Santos et al., 2014), JEV (Johari et al., 2012) and HCV (Bachmetov et al., 2012; Gonzalez et al., 2009). Associates of Phyllanthus species are studied as most important sources of bioactive metabolites that have antiviral effects for instance lignans, alkaloids and flavonoids for instance quercetin. They are able to occlude endogenous deoxyribonucleic acid, a polymerase of HBV, play significant role in multiplication of virus (Venkateswaran et al., 1987). Additionally, a range of bioactive metabolites of Phyllanthus niruri have been assessed for their reducing utilization of sera comprising of HBV surface antigen, gathered from chronic HBV infected patients (Thyagarajan et al., 1982). Moreover, a ninety-day management with extracts of plant effectively reduced the antigen of hepatitis B virus to untraceable levels among 2/3rd of hepatitis B virus-positive patients (Wang et al., 1995). Alkaloid extract of Phyllanthus niruri has also been stated to have a hindering and repressive effect on human immunodeficiency virus. These effects on multiplication of human immunodeficiency virus was considered by observing the reduction of HIV-prompted pathogenic modifications in human MT-4 cells, which demonstrated that these plant extracts show antiviral activity against the effect of pathogenic alterations, encouraged by human immunodeficiency virus on human MT-4 cells (Naik and Juvekar, 2003). American pokeweed, a powerful source of pokeweed antiviral protein and 3 isoforms of this protein have been acknowledged, precisely from spring leaves Pokeweed antiviral protein isoforms-I, primary summer leaves Pokeweed antiviral protein isoforms-II and late summer leaves Pokeweed antiviral protein isoforms-III which are similarly recognized as a category of RIPs and promotes depurination of genomic HIV-1 ribonucleic acid in a concentration-reliant way (Rajamohan et al., 1999). Correspondingly, Gelonium multiflorum and Momordica charantia are similarly contemplated as beneficial sources of an anti-HIV protein GAP31 and MAP30, which are like RIPs that have been recognized for their anti- human immunodeficiency virus strength (Schreiber et al., 1999). The plant of Rheum palmatum consists of organic aloe-emodin and anthraquinone used in Chinese medicine, active against influenza viruses, herpes simplex virus and cytomegalovirus (Sydiskis et al., 1991). Gallotannins, one of most powerful antiviral constituents recognize to suppress and reduce Epstein–Barr virus, wild-variety of herpes simplex virus-2, acyclovir-phosphonoacetic acid resilient herpes simplex virus-1, as well as thymidine kinase-deficient herpes simplex virus-1 (Hussain et al., 2017). Almost twenty percent of recognized botanicals have been utilized in pharmaceutical research projects, influencing the system of healthcare in constructive ways for instance managing cancer and injurious ailments (Naczk and Shahidi, 2006). Botanicals are capable of producing a huge amount of various bioactive constituents. High concentrations of plant-derived products, which may induce the damage of free radical, assembled in vegetables and fruits (Suffredini et al., 2004). Botanicals that comprise of useful plant chemicals may act as organic antioxidants in human body (Boots et al., 2008). Numerous research projects have discovered that lots of plants are affluent source of antioxidants. For example, phenolic compounds such as flavonoids, tannins, lignins, and vitamins A, C, E present in plants act as antioxidants (Suffredini et al., 2004). The intake of vegetables and fruits has been associated with numerous health values, an outcome of high dietary values and therapeutic properties (Valko et al., 2006). Ascorbic acid, beta carotene and lots of phenolics play active parts in decreasing inflammation, postponing aging, and averting certain kinds of carcinomas (Duthie et al., 1996). Escalating the ingestion of vegetables and fruits has been endorsed by numerous health care systems and agencies all over the world (Vivekananthan et al., 2003).

Conclusions and Recommendations

Among seven continents, in Asia, different types of flora is present which are the origin of several plant derived products with pharmacological importance, many of which contain antiviral substances. Identification of new plant-derived compounds with antiviral action is urgently needed and in high demand due to the prevalence of viral-related diseases as a worldwide health threat. Various chemicals presents in plants are useful against many viruses like rhinovirus, extremely contagious influenza virus, type-2 dengue virus, herpes simplex virus-1, adenovirus, poliovirus, RSV, EBV, JEV, and hepatitis C virus. Plant extracts and constituents are best choice in various viral infections instead of misuse of antibiotics. The intake of vegetables and fruits has been associated with numerous health values, an outcome of high dietary values and therapeutic properties. It would be more ideal if sophisticated pharmaceutical nanotechnologies and targeted methods are utilized that could help to utilize the natural herbal products for fighting against life-threatening viruses by evolving potent drugs which can act as adjuvant and protect the human-being from current and future pandemics.

Acknowledgments

AM would like to acknowledge the Principal, Mrinalini Datta Mahavidyapith, Birati, Kolkata 700051, India, for encouragement and necessary support.

Novelty Statement

In this review article we have tried to compile the available literature reporting antiviral plant products and herbal medicines active against different viral diseases. Traditional treatments for viral diseases not only constitute unique plant-based ‘lead molecules’ for discovering antiviral drugs, but also open up alternative strategies for management of viral infection. Each steps of viral life cycle is crucial for their sustenance, hence, could be considered as a prospective target for the development of antiviral therapeutics. Here we have selectively presented plant products / compounds in terms of these putative targets of antiviral mechanism of action, as described by the respective investigators.

Author’s Contribution

AM designed and implemented the idea of this manuscript. MA, MI, AM, RB, RZ, MTK, SR, PP and UL collected the information and wrote the article. RB revised the text under the supervision of AM. All authors approved the final version of the manuscript.

Conflict of interest

The authors have declared no conflict of interest.

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